Question: d percent of d

Comment on d percent of d

Do you have to use the p percent of x formula? Can you use the Part/Whole=Percent/100?
greenlight-admin's picture

No, that formula (Part/Whole = Percent/100) only works when we aren't trying to find some percent OF some value.

Thanks so much!


Great explanation! Now if the question were to ask bcd=4000, then would the answer be 2/5? Just trying to see if I got this right. Thanks!
greenlight-admin's picture

That's correct. If bcd = 4000, then we'd get 4000/10,000, which simplifies to 2/5

I worked this out in a different way and ended up with:
10% of 50 = 5.
5% of 5 = 2.5
This gives me the fraction: 5/2.
Is this incorrect? Thanks!
greenlight-admin's picture


Your solution is perfect until you got to "5% of 5 = 2.5"

You're correct to say that 10% of 50 = 5
From this, we can also say that 5% of 50 = 2.5
However, we cannot say that 5% of 5 = 2.5

Instead, let's think of it this way:
10% of 5 = 0.5
So, 5% of 5 = 0.25 = 1/4 (the correct answer)


Ha! Of course. Thank you for the explanation!

Hi Brent,
If I leave the answer as 1/4 in the exam, would that be a problem?
greenlight-admin's picture

A response of 1/4 would be perfect.

In fact, any fraction that equals 1/4 (e.g., 2/8, 25/100, 5/20, etc) would be considered correct.
For more on this, start watching the following video at 3:59:


Simply say b*c*d =2500 and b%c=d

=> b/100 * c =d => bc = 100*d--> step 1

=> substitute step 1 in given equation bcd=2500 as 100*d*d=25

=> d power 2 = 25 => d=|5|

=> now d%d means d/100 * d => 5/100*5 = 1/4
greenlight-admin's picture

Nice work!

what's s percent of r of 200 ?
greenlight-admin's picture

Does r represent a fraction (as in "What is s percent of 3/4 of 200?")
Or does r represent a percent (as in "What is s percent of 13 percent of 200?")

I'll answer both questions.

r represents a fraction: What is s percent of r of 200?
s percent of r of 200 = s/100 of (r of 200)
= s/100 of (200r)
= (s/100)(200r)
= 200sr/100
= sr

r represent a percent : What is s percent of r percent of 200?
s percent of r percent of 200 = s/100 of (r/100 of 200)
= s/100 of (r/100)(200)
= s/100 of (200r/100)
= s/100 of (2r)
= (s/100)(2r)
= 2sr/100
= sr/50

Aside: I could have used fewer steps, but played it safe :-)

Add a comment

Share the Love!

Tell the world that you just learned a nifty shortcut for dividing by 5 in your head. 

Let me Know

Have a suggestion to make the course even better? Email me today!

Free “Question of the Day” emails!